Means and method for removing casing from wells



Oct. 21, 1941. A w. RHLLAND MEANS AND METHOD FOR REMOVING CASING FROM WELLS riff. IA t i wills Filed July 2, 1940 Patented O ct. 2l, 194.1v

UNITED `STATES PATENT" OFFICE :MEAN S AND METHOD FOR REMOVNGAS- y ING FROM WELLS Willard P. Holland, Houston, Tex.

Application July 2, 1940, Serial No. 343,516

This invention' relates to means and method for removing casing from a well bore.-V

In drilling wells, particularly deep wells, a surface casing is first set. IIt isvusually of a length from several hundred feet to several thousand feet depending on the depth to whichitis conbe securely anchored to prevent a blowout in case high pressures are encountered in the well.

When the surface casing hasbeen lowered, and before the well bore has been reduced, cementitious material in plastic state is forced down through the casing, by conventional appliances for the purpose, and returns up about the casing the required distance, sometimes to the ground surface. The casing vas it is lowered is maintained approximately centered relative to the bore so that the cement around the casing will be of approximately uniform thickness. This cement, or cementitious material is then allowed to set and the casing is thereby securely anchored in the well so as not only to form a irm and secure anchorage for the well head equipment but .also to anchor the casing and equipment from being blown out in case strong well pressures are encountered.

'I'his cementitious material when it sets forms a cementitious shell around the casing which is frangible.

Upon completion of the well, if the well shoul prove non-productive the inner casing pipe, or other tubing, may be withdrawn from the well by conventional equipment provided for that purpose but it is usually impossible to withdraw the surface casing once it has been cemented. This surface casing represents a substantial investment and it is desirable that it be withdrawn from the well and salvaged in case the well is non-productive. A

It is a prime object of the present invention to provide means and a method for releasing the casing from its lsurrounding cementitlous shell which'anchorslit so that this surface casing can also be withdrawn for re-use.

With the -above and other objects in view the invention'has particular relation tol certain novel features of construction and use as well as to a novel method, an example of which is described Figure 1 shows a side elevation of the surface casing in a well bore showing also an inner casing and showing the cementitious shell around the surface casing in section, and

Figure 2 shows a fragmentary, sectional view of an explosive containing cartridge showing one means of exploding the charge.

ing wherein like numerals of'lreference designate the same parts in each of the figures, the numeral I designates a surface casing for a well having a guide shoe 2 on its lower end and supporting well head equipment 3 at its upper end. The surface casing I is shown located in the enlarged upper end 4 of the well bore 5. 'I'his casing I will usually range in length from 500 feet to 2500 feet although it is apparent that its length may vary within or beyond said limits.

When the enlarged portion 4 of the bore has reached the desired depth the casing I is then lowered into the bore to the bottom, care being taken to center the casing as accurately as possible in the bore.

A long cartridge shell, preferably in the form of` a tube 6, is then lowered into the enlarged portion of the bore alongside the casing and is spaced between the casing and the adjacent wall of the well by suitable cage-like spacers 1, 1. This cartridge shell is closed at the bottom in any preferred manner as by means of a plug 8 screwed therein.

Until itis to be used the upper end of the cartridge shell 6 may be closed by a cap 9. The enlarg'ed bore lV is then filled, on the outside of the casing, with cementitious material such as concrete III in which said casing as well as the cartridge shell Ii, is embedded. This cementi- 40 tious material is then allowed to set thereby anchoring the casing I securely in place.

When it becomes desirable to remove the-casing I from the wellan explosive charge such as II may be lowered into the tube, or cartridge shell, 6 thus forming a complete cartridge, said explosive charge being in the form of a fuse extending approximately from the lower to the upper end of the shell I0. Suitable means has been provided for exploding the charge I I. The force of the explosion will v occur throughout the length of the cartridge shell 6 and will completely shatter, or break up the frangible shell III surrounding the casing I' and saldshell will release its adherence to said vcasing `so that the surface casing will then be un- Referring now more particularly to the drawanchored and maybe pulled from the well by a conventional pipe pulling equipment provided for the purpose. l

A ny suitable means may be provided for exploding the charge. As shown there is a primer charge I2 conned within a suitable casing I 3 in the lower end of the cartridge shell. The ille.-

'ment Il of an electrical circuit `I5 extends through the primer charge. This circuit extends to the top of the ground and connected into it there is a source of electrical enei'gy'such as av 1; The method of removing a surface casingwhich is anchored in a well by means ora'cementitius shell around and adhering to the shellv and anchoring the shell to the walls of the well.

which method consistsin applying an explosive force to the shell to disrupt the shell approximately throughout the lensth thereof to release v it i'rom the casing and then withdrawing the released casing from the well.

2. The method oi removing a surface casingv which is anchored in a well by means of a cementitious shell around and adhering to the shell and anchoring the shell to the walls of the well, which method consists in applying an explosive force :to the shell approximately throughout the length thereof to shatter'the shell to release it from the casing and then withdrawing the released ca'sing from the Well.

3. Well equipment comprising a surface casing set inthe well bore, a shell of frangible material in the space between the casing and the walls of the well. means imbedded within the shell effective to disrupt the shell approximately throughout its length.

4. Well equipment comprising a surface casing in the well, an approximatelypcylindrical shell around the casing in the well bore adhering to so length, and means for exploding said charge.

WILLARD knol-LAND. 

